Oil-flooded screw compressors are designed with an oil separation system located on the discharge side of the compressor and comprise an oil receiver that cause most of the oil in the air stream to drop out and a coalescing filter pack, generally comprising one or two coalescing elements. The oil that is removed by the coalescing filter pack collects at the bottom of the elements and must be removed and returned to the compressor oil system. The oil is removed by a scavenge line that returns the oil to a low-pressure section of the compressor.
The pressure difference causes the oil to flow. The flow in the scavenge line must be regulated by an orifice to minimise the corresponding loss in compressor output. To prevent the orifice form plugging up, a strainer is used upstream of the orifice. To facilitate troubleshooting, a sight glass is also installed in the line to observe the flow of oil so that plugging of the strainer can be monitored.
Up until now, all of these components have been separate components connected together with pipe fittings. This arrangement has resulted in numerous leaks because of the number of pipe connections required.